The invention relates to a dissipative low-pass filter, more particularly for filtering power lines.
It is well-known that conventional non-dissipative low-pass filters, although they give satisfaction when the source and load impedances are fixed, generally speaking 50 Ohms, are not suitable for filtering power supply lines in which the impedance at high frequencies is not known and may vary.
It has already been proposed, in this case, to replace non-dissipative filters by dissipative filters or by active, complex filters. State-of-the-art dissipative filters are filters introducing losses in one of the branches of the filter. The introduction of losses in the inductive series branch of the filter, whether it be by use of the skin effect or by a dispersion in the magnetic material making up the inductance coil, has proved ineffective for frequencies lower than 5 MHz. Fitting a resistor in parallel on the inductance coil or a resistor in series with the capacitor does not solve the problem of load or source impedances either, as will be explained in more detail with reference to FIGS. 1 and 2.